The spiral on felt listed below is a blend of polyester and aramid. It is 2" (50mm) Wide and approximately 1/4" (7mm) thick. It is recommended for use on compression rolls only. To calculate required footage, multiply 0.2749 x roll length in inches x half of the roll diameter in inches and then round up to the nearest whole foot. For example, a 3-1/2" diameter, 120" long roll needs: 0.2749 x 120 x 1.75 = 57.7 or 58 feet.